This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Approximately 50 subjects will be enrolled in at least 3 treatment centers in the US. This study is expected to take about 12 months and the subjects will be actively involved for 28 weeks out of which 24 weeks are treatment period and a follow up period which occurs 4 weeks after the final treatment. The trial will include two subsets. In the first one, all subjects will be randomly assigned to receive weekly infusions of either the Kamada-API or Prolastin in a 2 to 1 fashion. That is for every two subjects randomly selected to receive Kamada-API one will be randomly selected to receive Prolastin. Following signing of an informed consent, screening procedures will be done, including vitals signs, medical history, physical examination, hematological and biochemical analyses, and virology blood draws. If applicable, subjects currently on API therapy will undergo a 5-week washout period during which they will receive no API. At least 6 subjects will be included.